Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-12-15
2001-11-20
Sterrett, Jeffrey (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S097000
Reexamination Certificate
active
06320766
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application entitled A POWER-SAVING CIRCUIT IN A AC/DC ADAPTER USED A MOBILE COMPUTER earlier filed in the Korean Industrial Property Office on the 31
st
day of July 2000, and there duly assigned Serial No. 2000-44394.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alternating/direct current (AC/DC) adaptor of a device, such as a portable computer, and more particularly to a power-saving circuit of an AC/DC adaptor for a device, such as a portable computer, capable of minimizing the power consumption of the AC/DC adaptor in a power-saving mode of the portable computer.
2. Description of the Related Art
In general, an AC/DC adaptor for a portable computer is a device which receives commercial alternating current (AC ) power, converts the AC power into a certain direct current (DC) voltage, and supplies the DC voltage to the portable computer. While the portable computer is widely used, technology relating to the AC/DC adaptor has rapidly advanced recently.
FIG. 1
is a view for explaining an AC/DC adaptor for a portable computer A. The portable computer A is connected by line B to an AC/DC adaptor C, the AC/DC adaptor C being connected by line B
1
to a plug D which engages an AC external power source outlet E. In case of a portable computer using a thin film transistor liquid crystal display (TFT-LCD), a DC voltage of 14V is required in general, so the AC/DC adaptor C receives the commercial AC power supply of 110V or 220V, converts the AC power supply into a DC voltage of 14V, and supplies the DC voltage to the portable computer A.
FIG. 2
is a circuit diagram for showing a conventional AC/DC adaptor, such as AC/DC adaptor C of
FIG. 1
, for a portable computer, such as portable computer A of FIG.
1
. The conventional AC/DC adaptor C for a portable computer in
FIG. 2
is constituted by an input unit
1
, a power transistor
2
, a transformer
3
, an output unit
4
, a feedback unit
5
, and a driver
6
. Operation of the conventional AC/DC adaptor C for a portable computer A will now be described with reference to FIG.
2
. First of all, a commercial AC power supply of 100V or 220V is applied to the input unit
1
. The input unit
1
converts the AC power supply into a DC voltage through an LC filter of capacitors C
1
, C
2
, and an inductance L
1
, a bridge diode D
1
, and a smoothing capacitor C
3
, and supplies the DC voltage to the primary coil P of the transformer
3
.
Continuing with reference to
FIG. 2
, at this time, if the power transistor
2
repeatedly switches on and off based on a pulse width modulation (PWM) control signal input from the driver
6
, an induced electromotive force from the primary coil P to the secondary coil S of the transformer
3
is generated. An AC voltage output from the secondary coil S of the transformer
3
is converted into a certain DC voltage (V
out
) of, in general, 14V through a rectifying diode D
2
and a smoothing capacitor C
4
of the output unit
4
, and the DC voltage is applied to a portable computer, such as portable computer A of FIG.
1
.
Further, with reference to
FIG. 2
, also at this time, a feedback unit
5
is, in general, provided to the AC/DC adaptor C for maintaining the output voltage of the output unit
4
at a certain voltage. air That is, the feedback unit
5
produces a feedback voltage based on the output voltage of the output unit
4
and outputs the feedback voltage to the driver
6
. The driver
6
compares the feedback voltage with a reference voltage, produces the PWM control signal, and supplies the PWM control signal to the power transistor
2
, so that the power transistor
2
is switched on and off. Accordingly, the output voltage of the AC/DC adaptor C is maintained at a constant voltage all the time to be supplied to a portable computer, such as portable computer C of FIG.
1
.
In general, if a user does not use a portable computer and the portable computer is also not turned off, the portable computer typically recognizes the state and reduces the power consumption of the portable computer itself to below a certain level, and, a display used by a user just before such power reduction typically appears automatically and instantly when the user wishes to again use the portable computer, differently from a turnoff of the power for the portable computer, as in the prior art. Such a portable computer having a power-saving function is realized with a display power management system (DPMS) according to a standard plan of the Video Electronics Standard Association (VESA), for example.
However, even though a portable computer carries out the power-saving mode, a conventional AC/DC adaptor for a portable computer is normally operated to supply a rating voltage to the portable computer, which can cause an unnecessary power loss in the AC/DC adaptor itself.
SUMMARY OF THE INVENTION
Accordingly, in order to solve the above problem, it is an object, among other objects, of the present invention to provide a power-saving circuit of an AC/DC adaptor for a portable computer, that drops down or lowers an output voltage in a power-saving mode of the portable computer while reducing a switching frequency of a power transistor.
In order to achieve the above object and other objects of the present invention, a power-saving circuit of an AC/DC adaptor for a portable computer, according to the present invention, includes an input unit for inputting a commercial AC voltage from an external AC voltage or power source and for converting the AC voltage into a DC voltage; a power transistor selectively switched on and offbased on a PWM control signal; a transformer for inputting the DC voltage from the input unit to a primary coil of the transformer and inducing an AC voltage at a secondary coil of the transformer based on a switch-on state and a switch-off state of the power transistor; an output unit for converting the AC voltage from the secondary coil of the transformer into a DC voltage to be output to a device, such as a portable computer; a feedback unit for producing a feedback voltage based on an output voltage of the output unit; and a driver for outputting to the power transistor the PWM control signal having a duty ratio controlled based on the feedback voltage from the feedback unit. The power-saving circuit of the present invention further includes an output load sensor for outputting a sensing signal if a sensed load of the output unit is below a predetermined level; an output voltage dropping unit for receiving the sensing signal when output by the output load sensor and for dropping an output voltage of the output unit based on the sensing signal when the sensing signal is received by the output voltage dropping unit; and a switching frequency reducer for receiving the sensing signal when output by the output load sensor and for reducing a switching frequency of the PWM control signal produced from the driver based on the sensing signal when the sensing signal is received by the switching frequency reducer.
Further, in order to achieve the above object among other objects of the present invention, another embodiment of a power-saving circuit of an AC/DC adaptor for a portable computer, according to the present invention, includes an input unit for inputting a commercial AC voltage from an external AC voltage or power source and for converting the AC voltage into a DC voltage; a power transistor selectively switched on and off based on a PWM control signal; a transformer for inputting the DC voltage from the input unit to a primary coil of the transformer and inducing an AC voltage at a secondary coil of the transformer based on a switch-on state and a switch-off state of the power transistor; a main voltage output unit for converting the AC voltage from a first secondary coil of the transformer into a DC voltage to be output to a device, such as a portable computer; a feedback unit for producing a feedback voltage bas
Bushnell , Esq. Robert E.
Samsung Electronics Co,. Ltd.
Sterrett Jeffrey
LandOfFree
Power-saving circuit for an AC/DC adaptor for a portable... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Power-saving circuit for an AC/DC adaptor for a portable..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power-saving circuit for an AC/DC adaptor for a portable... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2576012